The invention relates to commercial production and packaging of food products, and more particularly to application of materials such as antimycotic agents as surface treatments. The invention is particularly well-suited for application of natamycin, but may also be useful for application of other antimicrobial agents, or for application of other materials such as nutritional supplements, vitamins, other food additives, and colorants.
Application of natamycin to cheese shreds and small cubes has been accomplished by spraying a suspension of natamycin in an aqueous saline solution onto the shreds and cubes in a drum tumbler. For larger blocks of cheese, such as cheese chunks having a weight on the order of 8-12 oz., literature has recommended applying natamycin by dipping in a suspension of 1250 ppm natamycin, to provide a surface concentration of about 2.56-5.12 xcexcg/cm2 on most block cheeses. Higher surface concentrations of 5.12 xcexcg/cm2 or more have been recommended for blue cheese.
One commercial cheese chunk packaging system that has not included application of antimycotic agents is described below. The system includes stations for cutting, weighing, confirming absence of metal, and indexing the cheese chunks, then forming, filling and sealing the packages. The cutting step involves use of cutting equipment to divide a large (e.g., 680 lb.) block of cheese into a plurality of much smaller chunks of generally rectangular configuration. The chunks typically have a weight of about 10 oz. The chunks are then weighed, indexed, and conveyed to form/fill/seal apparatus that provides an individual hermetically sealed, gas-flushed package for each chunk. The operation is carried out at high speeds. The cheese chunks may travel, e.g., at about 145 ft./minute as they enter the form/fill/seal station.
One of the problems that must be addressed in application of liquids to food products in high speed packaging lines such as the one described above is avoidance of wetting of line components near the liquid application station. Application of liquid to food products can result in transfer of residue from the food products to downstream conveyors and other equipment. Also, liquid spray may be incidentally dispersed to upstream and downstream line components. This may interfere with proper operation of the equipment, and may present sanitation concerns. Saline solutions particularly can corrode conveyor bearings and other components of food-handling equipment. Another concern is that avoidance of microbial growth on the food product itself may be made more difficult where the food product has a wet exterior surface.
It is a general object of the invention to provide a commercial method and apparatus for surface treatment of food products that addresses the above problems.
The invention provides a method and apparatus for in-line application of a surface treatment to food products at a controlled rate in compliance with applicable food-handling equipment sanitation standards, wherein the rate of application is sufficient for efficacy of the surface treatment without resulting in transfer of unacceptable quantities of residue to adjacent line components, and wherein the material is applied without tumbling of the food products. The invention is particularly useful for spray application of a liquid antimycotic agent such as natamycin to cheese chunks, at a regulated predetermined rate to provide a sufficient surface concentration to inhibit mold growth on the surfaces of the cheese chunks throughout extended periods of exposure to ambient air, without unacceptable transfer of residue to adjacent components. The invention may also be useful for application of other antimicrobial agents, or for other materials such as nutritional supplements, vitamins, and colorants.
In one particular embodiment, the material applied comprises a suspension of natamycin in an aqueous saline solution. It has been found that mold growth on cheese chunks can be substantially inhibited by application of natamycin in accordance with the invention at surface concentration levels substantially lower than the recommended 2.56 xcexcg/cm2, and specifically levels as low as about 0.5 xcexcg/cm2 have been found to be effective in preventing mold growth on refrigerated cheese chunks exposed to ambient air for extended periods. In a preferred embodiment of the invention, the process applies an average surface concentration of about 1.0 to 1.1 xcexcg/cm2 to ensure that an adequate concentration is applied over substantially the entire exterior surface. Application of natamycian at these average surface concentrations with the apparatus of the invention ensures that substantially all of the cheese chunk surface area has a surface concentration of at least about 0.5 xcexcg/cm2.
The efficacy of an antimycotic agent may be measured in terms of the number of days during which mold growth is retarded in treated samples, relative to untreated control samples. Generally, if mold growth is retarded by 45 days or more, the antimycotic may be considered effective. The absolute length of time during which mold growth is delayed depends on the mold load in the ambient air, in addition to effects of antimycotic agents.
Application of antimycotic agent in accordance with the preferred embodiment of the invention has been effective in retarding mold growth by over 45 days, and has resulted in cheese chunks remaining mold-free for over 200 days in some cases, when refrigerated at typical refrigeration temperature of, e.g., 35xc2x0 F. to 45xc2x0 F., and exposed to ambient air.
The preferred embodiments involve application to cheddar cheese or other food products having similar antimycotic requirements. The invention may also be useful with food products having different antimycotic requirement, with appropriate adjustment of the process parameters. The apparatus is preferably compact so as to avoid adding unnecessarily to the floor space requirements of the packaging line. To this end, the apparatus preferably employs only three spray disks to provide substantially complete coverage of the cheese chunks.
The apparatus is preferably employed in line with equipment for cutting the cheese chunks from a larger block, then weighing the individual chunks, confirming absence of metal in the chunks, indexing the chunks, and forming, filling and sealing a hermetic, gas flushed individual package for each chunk.
The invention preferably employs a disk spray system, and preferably includes a conveyor having a gap between adjacent segments to permit application of spray from beneath the chunks as they traverse the gap.
To avoid penetration of the spray into the bearings of the conveyor shafts while also avoiding frictional impedance of shaft rotation, non-contacting interior shaft seals are preferably provided on the inside of the side walls at each end of one or more of the conveyor shafts. One or more of the conveyor shafts may also be provided with one or more grooves cooperating with surrounding shaft seals to inhibit flow of liquid toward the bearings.
To facilitate removal from the line for cleaning and/or maintenance, the apparatus preferably is movable, and to this end may be equipped with wheels, rollers, low friction sliders, or the like, and may be mounted on a track.
A spray enclosure is preferably provided to limit transfer of liquid spray to surrounding areas. The enclosure preferably surrounds the conveyor except for openings at the entrance and exit ends of the apparatus. To limit escape of fluid through these openings, the apparatus preferably includes means to remove liquid from the conveyor near its ends.
The apparatus preferably complies with USDA and Dairy 3A standards. To this end, interior components of the apparatus preferably are readily removable for cleaning. The conveyor preferably comprises an O-ring conveyor, with each segment comprising a plurality of O-rings under tension extending in parallel between a pair of rotary shafts that are disposed at its opposite ends. To reduce O-ring tension and bearing loads, the shafts at opposite ends of each conveyor segment may be driven in timed relation.
The apparatus preferably includes means for collecting excess spray, and the enclosure preferably includes a hood or housing. The hood includes means to direct fluid collected on interior surfaces thereof into the receptacle while preventing such fluid from dripping onto the food products, comprising one or more channels affixed to an interior surface of the hood. Each channel preferably has a minimum width sufficient to permit access by cleaning equipment and compliance with USDA and Dairy 3A standards.
Fluid collected for recirculation is preferably mixed with newly introduced fluid in a reservoir. A separation device such as a basket filter may be employed in the reservoir to facilitate separation of large particles of food product from the liquid collected, so that the liquid can be recirculated without entrainment of such food particles. Additional filtration may be provided at other locations in the recirculation system